Vacuum toilet with centrifugal separator

ABSTRACT

The invention relates to a vacuum toilet, comprising a toilet bowl with a bowl outlet opening, an intermediate tank with an inner wall surface enclosing an interior of the intermediate tank, an inlet opening formed on the intermediate tank, an outlet opening formed on the intermediate tank for connecting the interior of the intermediate tank to a wastewater container, a vacuum generator in fluidic communication with the interior of the intermediate tank for generating underpressure in said interior of the intermediate tank, a wastewater feed line which connects the bowl outlet opening to inlet opening and a wastewater tank which is in fluidic communication with the interior of the intermediate tank via the outlet opening. According to the invention, the inner wall of the intermediate tank, in at least one surface section, is formed in a rotationally symmetrical manner about an axis, and the inlet opening is arranged in said at least one surface section and has an orientation which defines an in-flow direction having a directional component tangential to said axis.

The invention relates to a vacuum toilet, comprising a toilet bowl witha bowl outlet opening, an intermediate tank with an inner wall surfaceenclosing an interior of the intermediate tank, an inlet opening formedon the intermediate tank, an outlet opening formed on the intermediatetank for connecting the interior of the intermediate tank to awastewater container, a vacuum generator in fluidic communication withthe interior of the intermediate tank for generating underpressure insaid interior of the intermediate tank, a wastewater feed line whichconnects the bowl outlet opening to inlet opening and a wastewater tankwhich is in fluidic communication with the interior of the intermediatetank via the outlet opening.

Vacuum toilets of the aforementioned type are specifically preferred invehicles, for example in buses, trains, airplanes and ships. Due to thecramped installation conditions that often prevail in such situations,and the absence of any differences in height, it is not possible forwastewater to be reliably discharged from the toilet bowl purely underthe force of gravity. The wastewater is therefore drawn out of thetoilet bowl by a vacuum and conveyed into a wastewater tank.

Central vacuum systems, so called, in which a vacuum is applied to thewastewater tank and the wastewater can then be conveyed out of thetoilet bowl into the wastewater tank via a switched valve in thewastewater pipe, are known from the prior art. However, the disadvantageof this solution is that a high vacuum is necessary, and that thewastewater tank must be designed to withstand the vacuum. It isgenerally desirable to operate the wastewater tank at atmosphericpressure to allow the wastewater tank to be of rugged construction tosuit the cramped construction space on board vehicles.

Vacuum toilet systems with an intermediate tank which is connectedbetween the toilet bowl and the wastewater tank in the direction ofwastewater flow are also known from the prior art. In these vacuumtoilets, an underpressure is firstly generated in the intermediate tankbefore the intermediate tank is then connected to the toilet bowl andthe wastewater is conveyed into the intermediate tank. The connection tothe toilet bowl is subsequently closed. Overpressure is then applied tothe intermediate tank and the wastewater is conveyed out of theintermediate tank into the wastewater tank. Although these vacuum toiletsystems allow the wastewater tank to be operated under atmosphericpressure, they require a substantial number of control valves to preventwastewater entering the underpressure conduits and the vacuum generator,and in order to carry out the sequence of underpressure andoverpressure.

The object of the invention is to provide a vacuum toilet system and adevice for discharging wastewater from a toilet bowl, which allowreliable operation with uncomplicated apparatus.

This object is achieved, according to the invention, with a vacuumtoilet designed as described at the outset, in which the inner wall ofthe intermediate tank, in at least one surface section, is formed in arotationally symmetrical manner about an axis, and the inlet opening isarranged in said at least one surface section and has an orientationwhich defines an in-flow direction having a directional componenttangential to said axis.

According to the invention, the wastewater is conveyed from the toiletbowl into the wastewater tank via an intermediate tank. To that end, avacuum is applied to the intermediate tank, and the wastewater isconveyed by this vacuum from the toilet bowl into the intermediate tank.According to the invention, the wastewater is fed into the intermediatetank in such a direction that it flows into a rotationally symmetricsection with a tangential directional component. Due to being fed intothe tank in this manner, the wastewater is guided by centrifugal forcesin a circular motion inside the intermediate tank and runs along theintermediate tank wall. An in-flow direction with a tangentialdirectional component should be understood here to mean an in-flowdirection oriented in such a way that the vector defined by thatdirection can be broken down so that a tangential vector componentensues. The in-flow direction can therefore include a radial or an axialdirectional component as well. However, it is preferred that the in-flowdirection does not include a radial directional component, or only aminimal one, but rather is predominantly tangential in orientation, withan additional axial directional component where relevant. Such anorientation of in-flow into the intermediate tank has proved to beparticularly advantageous for guiding the wastewater along the wall ofthe intermediate tank and through the interior of the intermediate tankto the outlet opening.

Thus, according to the invention, the wastewater is guided in a definedmanner inside the intermediate tank and along the wall thereof. Thisprevents any increased tendency of the wastewater in the intermediatetank to foam, for example, or to fill out the intermediate tank in anundefined manner by flowing into it in an undefined manner and/or byimpacting against the inner wall, from spraying or squirting aroundinside the intermediate tank, thus damaging the vacuum system andimpeding or preventing complete discharge of the wastewater from theintermediate tank.

A rotationally symmetric cross-section within the meaning of theinvention is to be specifically understood as a circular cross-sectionwhich allows rotary movement of the wastewater along the inner wall.Only the cross-section of the interior of the intermediate tank isrelevant in this regard, whereas the outer shape of the intermediatetank is of no relevance for that particular function and therefore doesnot need to be rotationally symmetric in shape. The advantages of theinvention are already achieved when the rotationally symmetric shape ispresent in an axially limited section of the intermediate tank in whichthe inlet opening is arranged, and other axial sections of theintermediate tank have a shape which is not rotationally symmetric. Aparticularly preferred embodiment, however, is one in which the entireintermediate tank is rotationally symmetric, or at least the region ofthe intermediate tank between the inlet and the outlet opening has aninner cross-section which is rotationally symmetric. The advantages ofthe invention are also achieved by cross-sections that deviate from thecircular shape, such as oval or elliptical cross-sections, for example,which are also to be understood as rotationally symmetric according tothe invention.

The in-flow direction can basically be defined by the orientation of theinlet opening, i.e. the position and orientation of the cross-section ofsaid inlet opening. According to the invention, however, the directionof flow is defined in a particularly advantageous and reliable mannerwhen the wastewater feed line opens into an inlet passage arrangedupstream and/or downstream from the inlet opening in the direction offlow and which defines a direction of flow into the interior of theintermediate tank, said direction defining a directional componenttangential to the axis. This development of the invention provides achannel which gives the wastewater flowing into the interior of theintermediate tank a defined in-flow direction. The channel may betangential in orientation, or may be oriented in a tangential-axialdirection, in a tangential-radial direction or have atangential-radial-axial orientation, wherein the tangential directionalcomponent according to the invention is meant to be more stronglypronounced than the axial or the radial directional component. Thechannel may extend into the interior of the tank or can be arrangedoutside the inside wall of the tank. By providing a channel, it ispossible for the opening into the interior of the tank to be designedflush with the wall of the intermediate tank, thus making it insensitiveto adherence of contamination.

The vacuum toilet according to the invention can be further developed byproviding a controllable closure valve in the wastewater feed line. Thecontrollable closure valve may be embodied as an electromagneticallyoperated valve or as a pneumatically operated valve and in a firstswitched state allows the wastewater feed line to be closed, and in asecond switched position for the wastewater feed line to be opened toproduce fluidic communication between the toilet bowl and theintermediate tank. The closure valve is preferably disposed adjacent toand at a small distance from the toilet bowl.

Another aspect of the invention is a wastewater facility for a vacuumtoilet, comprising an intermediate tank with a wall which encloses aninterior of the intermediate tank, an inlet opening formed on theintermediate tank for connecting the interior of the intermediate tankto a wastewater pipe, an outlet opening formed on the intermediate tankfor connecting the interior of the intermediate tank to a wastewatercontainer, a vacuum generator in fluidic communication with the interiorof the intermediate tank for generating underpressure in said interiorof the intermediate tank, in which the inner wall of the intermediatetank, in at least one surface section, is formed in a rotationallysymmetrical manner about an axis, and the inlet opening is arranged insaid at least one surface section and has an orientation which definesan in-flow direction having a directional component tangential to saidaxis. Such a wastewater facility thus includes the intermediate tank, inthe configuration according to the invention, and is suitable forinstallation in the vacuum toilet without necessarily having to replacethe toilet bowl and the wastewater tank. Existing vacuum toilets cantherefore be retrofitted in such a way, by installing the wastewaterfacility according to the invention, that the advantages of theinvention are achieved, by removing the intermediate tank already inplace and installing the wastewater facility according to the invention.It should be understood, as a basic principle, that the effects and theadvantage and the preferred embodiments and configurations of thefeatures of the wastewater facility according to the invention areachieved in the same manner and are to be understood in the same senseas previously described with regard to the vacuum toilet according tothe invention.

The wastewater facility according to the invention can be developed byproviding an inlet passage arranged upstream and/or downstream from theinlet opening in the direction of flow and which defines a direction offlow into the interior of the intermediate tank, said direction defininga directional component tangential to the axis. Such an inlet passage,which may be arranged inside, outside, or both inside and outside theinterior of the intermediate tank, achieves reliable definition of thein-flow direction with a predominantly or exclusively directionalcomponent in the same manner as the inlet channel previously describedfor the vacuum toilet according to the invention.

The vacuum toilet according to the invention, or the inventivewastewater facility with an inlet channel, can preferably be developedin such a way that the inlet passage defines the tangential in-flowdirection, in particular that the inlet passage runs in a tangentialdirection.

In this configuration, an exact tangential in-flow direction into theintermediate tank is defined by the inlet passage, thus achieving aparticularly advantageous wastewater flow path inside the intermediatetank.

The vacuum toilet and the wastewater facility can also be developed byhaving the axis extend in a direction with a vertical directionalcomponent, and preferably with vertical orientation, when theintermediate tank is installed. This orientation of the intermediatetank results in the axis of rotational symmetry of the intermediate tankbeing vertical or at least substantially vertical. With regard to itscirculating flow, the wastewater flowing into the tank can thereforeflow in a spiral pattern along the outer wall of the intermediate tank,substantially without disturbance and can continue flowing along thewall in the direction of gravity without detaching from the wall. Thisarrangement is preferred over horizontal or predominantly horizontalaxial orientations, because in the case of horizontally oriented axesthe wastewater might detach itself from the wall under the force ofgravity, in particular in the upper wall section of the intermediatetank, and would no longer maintain a rotationally symmetric flow alongthe inner wall of the intermediate tank. In particular when the axis hasa vertical directional component, or is vertical, the wastewater can beguided in a spiral movement from an inlet opening provided in the upperregion of the intermediate tank to an outlet opening provided in thelower region of the intermediate tank, along the wall of theintermediate tank from the inlet opening to the outlet opening, whichmeans that the wastewater does not perform any uncontrolled movementsinside the intermediate tank that might increase the amount ofcontamination and wastewater discharge.

It is still further preferred that the inlet opening defines atangential flow direction, in particular that the inlet opening has across-sectional area whose surface normal is tangential to the axis. Inthis embodiment, a tangential in-flow direction is defined by the inletopening, thus allowing the path taken by the wastewater inside theintermediate tank to be optimised. It should be understood that such adefinition of a tangential in-flow direction is influenced by the pathtaken by the cross-sectional area of the inlet opening and also by thegeometry of the cross-sectional area. For example, a cross-sectionalarea of oval-shaped cross-section and running flush with the wall of theintermediate tank can produce a tangential in-flow direction and allowthe wastewater feed line to be connected in a tangential direction, orfor a channel with a correspondingly tangential orientation to beprovided.

The vacuum toilet and the wastewater facility according to the inventioncan be further developed by the outlet opening having a gravity-actuatedclosure flap which is moved under the influence of gravity into a closedposition, held in said closed position by underpressure when anunderpressure in applied to the intermediate tank, and is moved into theopen position by the weight force of the wastewater when wastewater lieson a surface of the closure flap facing towards the interior of theintermediate tank.

In order to create a vacuum in the intermediate tank effectively, it isadvantageous and generally necessary in typical designs to close theoutlet opening so as to create a barrier between the intermediate tankand the wastewater tank. This barrier can basically be provided by meansof a valve, for example a pinch valve, or a valve which is switchedpneumatically or electromagnetically and has a sealing member whichslides or is moved in some other manner. According to one preferredembodiment according to the invention, the outlet opening is closed by aclosure flap which in a first position seals the outlet opening in aclosed position under the force of gravity or a spring force. This canbe achieved by bringing a circumferential sealing region of the closureflap into contact with a seal seat in the region of the outlet opening.Due to the pressures that are produced at the closure flap when creatinga vacuum inside the intermediate tank, an underpressure force acts onthe surface of the closure flap facing towards the intermediate tank,whereas atmospheric pressure is exerted on the side of the closure flapfacing towards the wastewater tank. As a result, the sealing effect canbe beneficially reinforced with increasing underpressure in theintermediate tank, and a seal is produced which allows the closure valvebetween the intermediate tank and the wastewater tank to be operated ina virtually wear-free manner with minimal actuation force. When theunderpressure inside the intermediate tank is removed, the reinforcementof the sealing effect is reduced or cancelled, and the closure flapcontinues to rest in the closed position solely by the force of gravityor the force of a spring, or a combination of the two. If there iswastewater in the intermediate tank at that time, a water column acts onthe surface of the closure flap facing towards the intermediate tank andpresses it into the open position, such that the wastewater from theintermediate tank can pass the closure flap and can flow into thewastewater tank. To achieve that purpose, it is advantageous if theweight or spring force that presses the closure flap into the closedposition be of such strength that it is less than the weight force of apredetermined residual volume of wastewater that may remain in theintermediate tank after emptying, for example a residual volumecorresponding to a water column of 1 to 5 cm, in particular of more than1 cm and preferably about 2 cm.

Actuation of the closure flap by the force of gravity can be achieved,for example, by the closure flap being pivotably mounted about an axisand the axis between a counterweight and the closure flap being arrangedin such a way that the counterweight actuates a closing movement of theclosure flap.

In the embodiment with the closure flap, it is further preferred thatthe gravity-actuated closure flap is mounted pivotably about a closureflap axis and has a sealing surface and a weight which presses saidsealing surface under the influence of gravity against a sealing facearranged around the outlet opening, or in that the closure flap operatedby spring force is pivotably mounted about a closure flap axis and has asealing surface and a spring element which presses said sealing surfaceunder the force of a spring against sealing surface arranged around theoutlet opening. These embodiments allow the closed position to bereturned efficaciously from the open position to the closed position,and it is possible to set a closed position in a reliable manner, whichcan then serve as a starting point for the self-reinforcing sealingeffect of the closure flap when creating a vacuum inside theintermediate tank. The weight can preferably be slidingly disposed on alever arm, in order to set the distance from the closure flap axis andthus to adjust the closure flap in respect of its closing force. Thespring used is preferably a helical spring or coil spring which producesa torque about the axis of the closure flap.

In the case of the embodiments provided with a closure flap, it isfurther preferred that the closure flap is arranged downstream in thedirection of flow from an outlet channel having a cross-sectional areawhich is smaller than the cross-sectional area of the intermediate tankin the region of the inlet opening. By providing such an outlet channelhaving a reduced cross-sectional area in comparison with thecross-sectional area of the intermediate tank in the region of the inletopening, a water column acting on the closure flap is effectivelycreated, with the result that the closure flap is impinged upon by thewastewater with a weight force that efficiently opens it. It ispreferred, as a basic principle, that the intermediate tank has a shapehaving a reduction in the cross-sectional area along a directionextending from the inlet to the outlet opening, for example with aconical geometry tapering towards the outlet opening.

According to another preferred embodiment, the closure flap has asurface which faces in the closed position towards the interior of theintermediate tank and has a surface normal with a vertical directionalcomponent and which is preferably vertical. This configuration of theclosure flap and its orientation allows the closure flap to be opened ina particularly effective manner under the force of gravity acting on thewastewater in the intermediate tank, which weighs on the closure flap.

According to another preferred embodiment, the interior of theintermediate tank has a rotationally symmetric outer cross-section inthe region of the surface section where the inner wall of theintermediate tank is rotationally symmetric. In this embodiment, theinterior of the intermediate tank is rotationally symmetric over itsentire circumference, over an axial region or over the entire length ofthe intermediate tank.

The vacuum toilet and the wastewater facility according to the inventioncan be further developed by the diameter of the outer cross-section inthe rotationally symmetric region of the inner wall surface of theintermediate tank decreasing in the direction of gravity, the inletopening preferably being arranged at the upper end of the rotationallysymmetric inner wall surface of the intermediate tank, viewed in thedirection of gravity. It is preferred, as a basic principle, that at therotationally symmetric section of the intermediate tank tapers in itscross-sectional area in a direction from the inlet to the outletopening, and preferably that the entire intermediate tank tapers in itscross-sectional area from the inlet opening to the outlet opening. Suchan intermediate tank design makes up for the decrease in flow velocitycaused by frictional losses of the wastewater at the external wall, byproviding a reduction in the radius with which the wastewater circulatesabout the axis of the intermediate tank, thus preventing the wastewaterfrom detaching itself from the intermediate tank wall. At the same time,a water column acting on the closure flap is effectively created due totapering of the intermediate tank in the direction of the outletopening, thus causing the closure flap to open under the force ofgravity in a reliable manner of operation, without large residualamounts of wastewater remaining inside the intermediate tank when theclosure flap closes again after the wastewater has passed through intothe wastewater tank. The outlet channel may be formed with a constantdiameter along its length, or with a varying diameter. Moreparticularly, the outlet channel can also taper conically in thedirection of the closure flap, or have a cross-sectional enlargement inthe direction of the closure flap, in order to prevent any clogging inthe region of the closure flap.

It is further preferred that the vacuum toilet or the wastewaterfacility according to the invention be developed such that the entireintermediate tank is rotationally symmetric. A rotationally symmetricshape should be understood in this case, as already described in theforegoing, as one where the inner cross-sectional area of the interiorof the intermediate tank is rotationally symmetric about a longitudinalaxis of the intermediate tank, whereas the outer surface of theintermediate tank can be freely designed in that respect and may haverotational symmetry or a shape that is not rotationally symmetric. Arotationally symmetric design may be a shape of circular cross-section,but according to the invention may also include shapes that depart fromthe circular and are in the shape of oval or elliptical cross-sectionalareas.

Finally, according to another preferred embodiment of the vacuum toiletor the wastewater facility according to the invention, the vacuumgenerator is arranged in the interior of the intermediate tank by meansof an ejector orifice and said ejector orifice is connected to theregion of the intermediate tank axis and preferably coaxially with theintermediate tank axis. This embodiment provides an advantageousarrangement of the ejector orifice in a region which is typically notexposed to wastewater, due to the shape in which the wastewater movesinside the intermediate tank, so that the risk of wastewater enteringthe vacuum generator can be significantly reduced or entirely avoided.The ejector orifice may be radial in orientation, for example, and anaxial orientation or a radial-axial orientation can also be provided.Inside the intermediate tank, more specifically, the entire vacuumgenerator may be arranged in the region of the axis, for example in theform of a Venturi-type ejector connected to a source of compressed airfor generating the vacuum. This allows the intermediate tank with thevacuum generator to be of compact design. Depending on the specificinstallation situation and access to systems already existing inside thevehicle, other configurations are also basically possible, for exampleconnecting a vacuum port that opens into the intermediate tank to acentral vacuum system, or a vacuum generator that is a central componentof the vacuum toilet.

It is still further preferred that the rotationally symmetric wallsection is formed at an insert member and the intermediate tank has anexternal wall which surrounds said insert member. In this configuration,the intermediate tank is double-walled in sections thereof. Thewastewater feed line opens into the insert member, in which vacuumextraction is also carried out in an advantageous manner. In this way,it is possible for the underpressure for sucking out the wastewater tobe created and maintained better.

Another aspect of the invention is a method for controlling a vacuumtoilet, comprising the steps of: generating an underpressure in theinterior of an intermediate tank by means of a vacuum generator, openingan outlet valve in a wastewater feed line which connects a toilet bowlto the interior of the intermediate tank, feeding an amount ofwastewater out of the toilet bowl via the wastewater feed line into theinterior of the intermediate tank, the interior of the intermediate tankbeing enclosed by an inner wall surface which is arranged rotationallysymmetrically about an axis, and the wastewater being fed into theinterior of the intermediate tank with a tangential directionalcomponent and preferably in the tangential direction in relation to saidaxis.

The method can be developed by the wastewater from the interior of theintermediate tank flowing in front of an outlet opening and accumulatingin front of said outlet opening, and the outlet opening being sealed bya closure element which is moved from a closed position into an openposition when the weight force of the wastewater exceeds a predeterminedvalue.

The method can be developed by the closure element being a pivotablymounted flap which is moved into the closed position by a counterweight.

The method described in the foregoing can be carried out using thevacuum toilet according to the invention. The preferred embodiments ofthe vacuum toilet and its manner of operation, as previously described,therefore provide further development of the method according to theinvention.

Preferred embodiments of the invention shall now be described in greaterdetail with reference to the attached Figures, in which:

FIG. 1: shows a schematic side view of a first preferred embodiment,

FIG. 2: shows a schematic top view of a part of the embodiment accordingto FIG. 1 in a cutaway view along line A-A in FIG. 1,

FIG. 3: shows a schematic side view of a second preferred embodiment;and

FIG. 4: shows a schematic top view of a part of the embodiment accordingto FIG. 3 in a cutaway view along line A-A in FIG. 3.

The vacuum toilet shown in FIG. 1 comprises a toilet bowl 10 with a bowloutlet opening 11 which opens into a wastewater feed line 12. Inwastewater feed line 12, a pneumatically operated shut-off valve 20which can block or release flow through wastewater feed line 12 isarranged adjacent to bowl outlet opening 11.

Wastewater feed line 12 opens into an intermediate tank 30. Intermediatetank 30 has a funnel shape and is formed in a rotationally symmetricalmanner about an axis 31. When installed as shown, intermediate tank 30is arranged such axis 31 is vertically oriented, that is to say itextends in the direction of gravity.

Intermediate tank 30 has an interior 32 which is laterally defined by aconical intermediate tank wall 33. At its top end, intermediate tank 30is closed by a circular lid 34.

Intermediate tank 30 is subdivided in an upper section 30 a and a lowersection 30 b. The upper section has a shape which tapers conicallydownwards in the direction of vertical axis 31. The lower section, whichis joined flush with the upper section, is in the shape of a cylindricalchannel.

At the bottom end of lower section 30 b, a closure flap 60 is arrangedwhich closes an outlet opening 35 at the bottom end of the intermediatetank. In the closed position, closure flap 60 is slantingly oriented inrelation to the direction of gravity, and in the embodiment shown, theclosure flap extends in the closed position at an angle of 45° to thedirection of gravity. Closure flap 60 is mounted pivotably about aclosure flap axis 61 and is pressed by means of a counterweight 62 intothe closed position against the wall sections of intermediate tank 30that defined the outlet opening.

Most of the lower section 30 b of the intermediate tank, as well asclosure flap 60 with its pivot axis 61 and counterweight 62, arearranged inside a wastewater tank 50, into which the wastewater isemptied from intermediate tank 30.

A central opening into which a vacuum generator 40 is sealingly insertedis provided in upper lid 34 of intermediate tank 30. Vacuum generator 40is embodied as an ejector with a compressed air connection 41 andgenerates a vacuum by applying the Venturi effect to produce anunderpressure and to suck air through an ejector orifice 42 arranged atthe bottom end of ejector 40 and coaxial with the longitudinal axis 31of intermediate tank 30.

Wastewater feed line 12 opens into intermediate tank 30 in the upperregion of the intermediate tank at approximately the height of orifice42 of ejector 40. As can be seen from the cross-sectional top view shownin FIG. 2, wastewater feed line 12 initially extends radially inrelation to longitudinal axis 31 and then opens into a channel section36 which extends in a direction tangential to longitudinal axis 31.Channel section 36 opens into an opening 37 which is flush withfunnel-shaped wall 33 and allows the wastewater to flow in a tangentialdirection into the interior 32 of the intermediate tank. The wastewatertherefore runs in an increasingly tight spiral starting from inletopening 37 and downwards along the inner wall of the intermediate tankas shown by the broken line in FIG. 1 and by arrows in FIG. 2. Thewastewater does not come into contact with ejector 40 or ejector orifice42, therefore, but runs along a defined path in the direction of lowersection 30 b of intermediate tank 30. The wastewater collects in thislower section 30 b.

As soon as the interior 32 of the intermediate tank is vented viaejector 40 or by some other vent opening, therefore causing theunderpressure in the intermediate tank 30 to decrease and to approachthe ambient pressure, closure flap 60 is no longer held in the closedposition by the underpressure in interior 32 of the intermediate tank,and the weight force of the wastewater that has collected around thebottom section 30 b of the intermediate tank presses closure flap 60into the open position. The wastewater can therefore flow, under theforce of gravity and under the atmospheric pressure in the intermediatetank and the wastewater tank, into wastewater tank 50. As soon as thewastewater has flowed out of the intermediate tank, closure flap 60 ispivoted back into the closed position by counterweight 62 and sealsoutlet opening 35.

A flushing operation according to the inventive vacuum toilet andwastewater facility is thus carried out in the following way. Thewastewater firstly collects in toilet bowl 11, in front of the closedshut-off valve 20. When a flushing operation is initiated, flushingfluid is preferably sprayed into the toilet bowl, first of all. At thesame time, an underpressure which pulls closure flap 60 into secureclosure on outlet opening 35 is then created in intermediate tank 30 bymeans of ejector 40. After shut-off valve 20 has been opened, thewastewater is sucked into the interior 32 of the intermediate tank bythe underpressure in intermediate tank 30, then runs in a spiral alongtank wall 33 and collects in the lower section 30 b of the intermediatetank. Shut-off valve 20 can then close again on a time-controlled basisor after the wastewater has passed through. However, shut-off valve 20can also be kept open for longer, so that it causes the interior 32 ofthe intermediate tank to be ventilated via bowl outlet opening 11 afterthe wastewater has passed through. If shut-off valve 20 is closed, thisventilation can also be carried out, alternatively, via some otherventilation opening or via ejector 40. Ejector 40 is time-controlled, oris switched off once a particular underpressure has been reached in theinterior of the intermediate tank, and subsequently does not create anyfurther underpressure in the interior 32 of the intermediate tank. Assoon as the interior 32 of the intermediate tank has been ventilated,the wastewater that has collected in the interior 32 of the intermediatetank pushes closure flap 60 open and flows into wastewater tank 50.After the wastewater has passed through, closure flap 60 is pressed bycounterweight 62 back into the closed position. The vacuum toilet isthen ready for the next flushing operation.

FIGS. 3 and 4 show a side view and a top view of the intermediate tankin a second embodiment of the invention. In this embodiment, anintermediate tank 130 is connected to a wastewater feed line 112. Theintermediate tank is delimited from the surroundings by an outer housingwall 138. The shape of the outer housing wall can be designedsubstantially freely with regard to its inner surface and its externalsurface, since they are not a main factor affecting the flow anddischarge conditions in the interior of the intermediate tank.

A conical feed funnel 133 is arranged in the interior of theintermediate tank and extends along a vertical longitudinal axis 100 andtapers conically from top to bottom. Wastewater feed line 112 opens intothe conical feed funnel in a tangential direction relative tolongitudinal axis 100.

An ejector 140 is arranged inside conical feed funnel 133. The ejectoris concentric with longitudinal axis 100 and extends along saidlongitudinal axis 100. An axially oriented ejector orifice 141, throughwhich air is sucked out of the interior of the intake funnel, isarranged at the bottom end of the ejector. A bottom outlet opening 134of the intake funnel opens into the intermediate tank section that isenclosed by outer housing wall 138.

Wastewater flowing through the wastewater feed line into theintermediate tank according to the second embodiment is introducedtangentially into the conical intake funnel and flows inside theinterior 132 of the intake funnel along the inner wall of the intakefunnel and downwards along a spiral flow path to the outlet opening 134of the funnel. The wastewater passes through the outlet opening of thefunnel and collects in interior section 132 a of the intermediate tankbefore an outlet opening 135 at the bottom end of the intermediate tank.

Like outlet opening 35 of the first embodiment, outlet opening 135 canbe closed by a gravity-actuated valve and be opened by the weight forceof the wastewater that collects in the intermediate tank. In theembodiment shown above, outlet opening 135 is closed by a pneumaticallyoperated hose valve 160. When a positive air pressure is applied to hosevalve 160 through a pneumatic line 161, the valve closes, and if no suchoverpressure is applied, hose valve 160 opens.

Improved extraction is achieved with the second embodiment, due to thearrangement of the ejector inside an enclosed region in the intermediatetank. At the same time, the advantages deriving from the wastewaterbeing discharged with spiral motion inside the intermediate tank due toits tangential in-flow are retained, and contamination of the ejector isavoided as a result of guiding the wastewater flow in this manner.

1. A vacuum toilet, comprising: a toilet bowl with a bowl outletopening, an intermediate tank with an inner wall surface enclosing aninterior of the intermediate tank, an inlet opening formed on theintermediate tank, an outlet opening formed on the intermediate tank forconnecting the interior of the intermediate tank to a wastewatercontainer, a vacuum generator in fluidic communication with the interiorof the intermediate tank for generating underpressure in said interiorof the intermediate tank a wastewater feed line which connects the bowloutlet opening to inlet opening, a wastewater tank which is in fluidiccommunication with the interior of the intermediate tank via the outletopening, characterised in that the inner wall surface of theintermediate tank, in at least one surface section, is formed in arotationally symmetrical manner about an axis, and the inlet opening isarranged in said at least one surface section and has an orientationwhich defines an in-flow direction having a directional componenttangential to said axis.
 2. The vacuum toilet according to claim 1,characterised in that the wastewater feed line opens into an inletpassage arranged upstream and/or downstream from the inlet opening inthe direction of flow and which defines a direction of flow into theinterior of the intermediate tank, said direction defining a directionalcomponent tangential to the axis.
 3. The vacuum toilet according toclaim 1, characterised by a controllable closure valve in the wastewaterfeed line.
 4. A wastewater facility for a vacuum toilet, comprising: anintermediate tank with a wall enclosing an interior of the intermediatetank, an inlet opening formed on the intermediate tank, for connectingthe interior of the intermediate tank to a wastewater feed line an inletopening formed on the intermediate tank, for connecting the interior ofthe intermediate tank to a wastewater tank, a vacuum generator influidic communication with the interior of the intermediate tank forgenerating underpressure in said interior of the intermediate tankcharacterised in that the inner wall surface of the intermediate tank,in at least one surface section, is formed in a rotationally symmetricalmanner about an axis, and the inlet opening is arranged in said at leastone surface section and has an orientation which defines an in-flowdirection having a directional component tangential to said axis.
 5. Thewastewater facility according to claim 4, characterised by an inletpassage arranged upstream and/or downstream from the inlet opening inthe direction of flow and which defines a direction of flow into theinterior of the intermediate tank, said direction defining a directionalcomponent tangential to the axis.
 6. The vacuum toilet according toclaim 2, characterised in that the inlet passage defines a tangentialflow direction defined, in particular in that the inlet passage runs ina tangential direction.
 7. The vacuum toilet according to claim 1,characterised in that, when the intermediate tank is installed, the axisextends in a direction with a vertical directional component, and ispreferably vertical in orientation.
 8. The vacuum toilet according toclaim 1, characterised in that the inlet opening defines a tangentialflow direction, in particular that the inlet opening has across-sectional area whose surface normal is tangential to the axis. 9.The vacuum toilet according to claim 1, characterised in that the outletopening has a gravity-actuated closure flap which is moved under theinfluence of gravity into a closed position, held in said closedposition by underpressure when an underpressure in applied to theintermediate tank, and is moved into the open position by the weightforce of the wastewater when wastewater lies on a surface of the closureflap facing towards the interior of the intermediate tank.
 10. Thevacuum toilet according to claim 9, characterised in that thegravity-actuated closure flap is mounted pivotably about a closure flapaxis and has a sealing surface and a weight which presses said sealingsurface under the influence of gravity against a sealing face arrangedaround the outlet opening, or in that the closure flap operated byspring force is pivotably mounted about a closure flap axis and has asealing surface and a spring element which presses said sealing surfaceunder the force of a spring against sealing surface arranged around theoutlet opening.
 11. The vacuum toilet according to claim 9,characterised in that the closure flap is arranged downstream in thedirection of flow from an outlet channel having a cross-sectional areawhich is smaller than the cross-sectional area of the intermediate tankin the region of the inlet opening.
 12. The vacuum toilet according toclaim 9, characterised in that the closure flap has a surface whichfaces in the closed position towards the interior of the intermediatetank and has a surface normal with a vertical directional component andwhich is preferably vertical.
 13. The vacuum toilet according to claim1, characterised in that the interior of the intermediate tank has arotationally symmetric outer cross-section in the region of the surfacesection where the inner wall of the intermediate tank is rotationallysymmetric.
 14. The vacuum toilet according to claim 13, characterised inthat the diameter of the outer cross-section in the rotationallysymmetric region of the inner wall surface of the intermediate tankdecreases in the direction of gravity, the inlet opening preferablybeing arranged at the upper end of the rotationally symmetric inner wallsurface of the intermediate tank, viewed in the direction of gravity.15. The vacuum toilet according to claim 1, characterised in that theentire intermediate tank is rotationally symmetric.
 16. The vacuumtoilet according to claim 1, characterised in that the vacuum generatoris connected to the interior of the intermediate tank by means of anejector orifice and said ejector orifice is arranged in the region ofthe intermediate tank axis and preferably coaxially with theintermediate tank axis.
 17. The vacuum toilet according to claim 1,characterised in that the rotationally symmetric wall section is formedat an insert member and the intermediate tank has an external wall whichsurrounds said insert member.
 18. A method for controlling a vacuumtoilet, comprising the steps of: generating an underpressure in theinterior of an intermediate tank by means of a vacuum generator, openingan outlet valve in a wastewater feed line which connects a toilet bowlto the interior of the intermediate tank, feeding an amount ofwastewater out of the toilet bowl via the wastewater feed line into theinterior of the intermediate tank, characterised in that the interior ofthe intermediate tank is enclosed by an inner wall surface which isarranged rotationally symmetrically about an axis, and the wastewater isfed into the interior of the intermediate tank with a tangentialdirectional component and preferably in the tangential direction inrelation to said axis.
 19. The method according to claim 18,characterised in that the wastewater from the interior of theintermediate tank flows in front of an outlet opening and accumulates infront of said outlet opening, and that the outlet opening is sealed by aclosure element which is moved from a closed position into an openposition when the weight force of the wastewater exceeds a predeterminedvalue.
 20. The method according to claim 19, characterised in that theclosure element is a pivotably mounted flap which is moved into theclosed position by a counterweight.